This invention relates generally to seat assemblies, and more particularly to a vehicle seat assembly having the function of sensing and weighing an occupant seated on the seat of a vehicle.
Conventionally, an air bag system (hereinafter referred simply to “air bag”) equipped inside a vehicle, typically mounted under the dashboard for front-seat passengers, or on the back of the front seat of the vehicle for rear-seat passengers, is controlled so that whether to actuate the air bag in a collision or the like and how rapidly to allow the air bag if actuated to inflate are determined in accordance with the status of the seat as represented by whether a given seat is occupied and how much an occupant if any weighs. For example, control is exercised such that if the seat is occupied by an adult or an adolescent (older child), the air bag is actuated, but if the seat is unoccupied or occupied by a baby (infant) or toddler secured in a child safety seat (child restraint), the air bag is not actuated; and when the air bag is actuated, if the seat is occupied by an adult or well-built adolescent, the air bag is actuated at a higher speed, but if the seat is occupied by a small child, the air bag is actuated at a lower speed. This allows an air bag to exercise an optimum restraint on an occupant to be protected in a collision or the like, according to the status of the seat for which the air bag is provided, and addresses the need for preventing an unnecessary deployment of an air bag corresponding to the unoccupied seat or the seat occupied by an infant or toddler occupying a child safety seat.
In order to exercise an adequate control over the operation of an air bag, seat assemblies having the function of sensing the weight of an occupant seated on the seat have been proposed. For example, one or more weight sensors is typically mounted in such a position under a seat as to move together with the seat as the seat slides in front/rear directions. Instead, disclosed in JP 11-94637 A is a seat occupant sensing system having a load cell (weight sensor) provided in a fixed position at a floor of the vehicle but the weight is measured from the shift amount of a bucket-shaped weight-receiving member that supports the seat, and the weight-receiving member thus appears to move together with the seat as the seat slides in front/rear directions.
To be more specific, referring now to FIG. 8, which is a schematic illustration, in perspective, of an exemplary conventional seat assembly 100 as viewed obliquely from a rear seat, a passenger seat 101 (front seat) installed in a vehicle (placed on a floor F at the left side of its cabin) is occupied by a child safety seat 111, which is fastened by a seat belt device 102 using a belt insertion hole 112 provided in the child safety seat 111. The belt insertion hole 112 is a through hole perforated from side to side through the seat back of child safety seat 111. The seat belt device 102 for the seat 101 basically includes a seat belt anchor 104 provided on a widthwise outward edge of the floor F at the rear of the seat 101, a buckle 117 provided on a rear lower portion of a side of the seat 101 facing toward an inside of the vehicle, a slip guide 108 provided on an upper portion of a center pillar 103 of the vehicle, a retractor 106 provided on a lower portion of the center pillar 103, a seat belt, and a tongue 109 having a hole through which the seat belt is slidably threaded. The seat belt extends from the seat belt anchor 104, passing through the belt insertion hole 112 provided in the child safety seat 111, routed through the hole of the tongue 109 latched in the buckle 117, passing again through the belt insertion hole 112, and routed through a hole in the slip guide 108, and to the retractor 106 into which the seat belt may be retracted. Principal portion of the seat belt is comprised of a lap belt 105 extending between the seat belt anchor 104 and the tongue 109, and a shoulder belt 107 extending between the tongue 109 and the slip guide 108. A limit switch 113 provided in the retractor 106 serves to give a proper tension to the seat belt to facilitate handling thereof and to have an adequate restraint applied to an occupant. Since the seat belt anchor 104 is positioned at an adequately lower level and at the rearward of the seat 101 as shown in FIG. 8 (typically fastened with a bolt 39 on the floor F of the vehicle as shown in FIG. 9), the lap belt 105 of which one end is anchored to the seat belt anchor 104 and the other end is threaded through the hole of the tongue 109 to extend, as a shoulder belt 107, toward a slip guide 108 is configured to be held under a proper tension constantly giving an adequate downward and rearward stress for restraint of the occupant (or the child safety seat 111). As shown in FIG. 9, the seat assembly 100 also includes a guide rail 131 for guiding a front/rear movement of the seat 101. The guide rail 131 is provided under the seat 101 so as to receive a slider (not shown) fixed to the seat 101 for allowing the seat 101 to slide along the guide rail 131. In this construction, it might be conceptually conceivable, as illustrated in FIG. 9, (though it may appear impractical for reasons as will be described below) that a weight sensor 120 could be provided under the guide rail 131, and that a leg 116 could be provided under the weight sensor 120.
However, in this conceptual seat assembly 100, if the seat belt were buckled up to fasten to the seat 101 an occupant or a child safety seat with a child occupant seated therein, the tension of the lap belt 105 would press the seat cushion of the seat 101 toward the floor F of the vehicle, disadvantageously affecting the weight sensor 120, so that the weight sensor 120 would sense a load more than the weight of the occupant and generate a wrong signal as indicative of the status of the seat 101. Namely, it is understood that provision of the weight sensor 120 in the conventional seat assembly 100 in such a manner as discussed above should necessitate an extra mechanism for correcting the signal output from the weight sensor 120 on the basis of the action of the lap belt 105. Another disadvantage inherent in the above-discussed seat assembly 100 would be that, in cases where the seat assembly is applied to a two-door vehicle, when the seat 101 is slid frontward with its seat back tilted forward and/or its seat bottom tilted up to make a path for a person who wishes to get into the rear seat, the seat belt (especially, lap belt 105 laid across the path to the rear seat) obstructs the passage of the person, with the result that the person cannot easily get into or out of the rear seat.
Illustrative, non-limiting embodiments of the present invention overcome the above disadvantages and other disadvantages not described above. Also, the present invention is not required to overcome the disadvantages described above, and an illustrative, non-limiting embodiment of the present invention may not overcome any of the problems described above.